I will start thinking Bitcoin is dead when I need to exchange my Bitcoins to other altcoin when I using (spending) my Bitcoins. Not happening today. All I see some altcoin prices up (some > 10x in few months), yet their real useability is almost the same - clear sign of speculation bubble to me.
Yes I do this also if bitcoin dead I will exchange my bitcoin in to the other altcoin because I know when bitcoins deads theres a new coin that will become #1 like the bitcoin. But as of now bitcoin price not dead or not going dead bitcoin as of now have stable price and increasing everyday and every month.